( Reaffirmed 2006 ) IS : 2165 ( Part 2 ) - 1983 Indian Standard INSULATION CO-ORDINATION PART 2 PHASE-TO-PHASE INSULATION CO-ORDINATION, PRINCIPLES AND RULES High Voltage Techniques Sectional Committee, ETDC Chairman DR B. I. GTJRURAJ Members DR G. R. NAQABHUSRA~A ( Alternate to Dr B. I. Gururaj ) ' Calcutta Electric Supply Corporation Ltd, Calcutta SHRIA. K. BARMAN SRRI S. MUKHOPADHYAY ( Alternate ) DR S. C. BHATIA Siemens India Ltd, Born bay SHRI V. T. D'SILVA ( ALternate ) Punjab State Electricity Board, Patiala SHRI A. K. CHOPRA SHRIP. S. SATNAM ( Alternate) Jyoti Ltd, Vadodara SRRIV. B. DESAI DR V. N. MALLER ( Alternate ) Central Power Research Institute, Bangalore DIRECTOR SENIOR DEPUTY DIRECTOR ( Alternate ) Central Electricity Authority, New Delhi DIRECTOR ( EHV ) DIRECTOR ( SUB-STATION ) ( Alternate ) National Thermal Power Corporation Ltd, SHRI P. K. DWIVEDI New Delhi SHRI N. V. RAO ( Alternate ) Organization, Research Designs & Standards JOINT DIRECTOR STANDARDS Ministry of Railways, Lucknow ( TI-I ) DEPUTY DIRECTOR STANDARDS ( E ) Cs ( Alternate ) Tata Hydro-Electric Power Supply Co Ltd, Bombay SHRIV. N. MANOHAB SHRI G. K. VENKATA RAO ( Alternate ) U. P. State Electricity Board, Lucknow SHRI MATA PRAEAD SRRI S. C. AGARWAL ( Alternate ) Tamil Nadu Electricity Board, Madras MISS MARY MATHEW SHRI S. KRISHNARAJ ( Alternate ) National Test House, Calcutta SHRI S. K. MUKHERJEE SHRI R. N. MUKHERJ~E ( Alternate ) Bombay Electric Supply & Transport Undertaking, SHRI V. H. NAVKAL Bombay SHRI M. L. DONGRE ( Alternate ) ( Continued on page 2 ) @ Copyright 1988 INDIAN STANDARDS INSTITUTION Tbis publication is protected under the Indian Cofiyright Act ( XIV of 1957 ) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act. Representing Indian Institute of Science, Bangalore 19 IS : 2165 ( Part 2 ) - 1983 ( Continuedfrom page 1 ) Members Representing SHRI S. D. PALIWAL Bharat Heavy Electricals Ltd, New Delhi SH~I B. N. GHOSH ( Alternate I ) SHRI K. NATARaJAN ( &tern& II ) Hindustan Brown Boveri Ltd, Bombay SHRI S. R. POTNIS SHRI V. S. MANI ( Alternate ) Electrical Research & Development Association, DR K. V. N. Rae Vadodara SHKI P. K. JOSHI ( Alternate ) Maharashtra State Electricity Board, Bombay REPRESENTATIVE SHRI K. S. SIVaI'RAKASAM Karnataka Electricity Board, Bangalore SHRI H. M. S. LINGIAH ( Alternate ) U. P. Government Pottery Development Centre, SHRI SURENDRA SINCH Khurja SHRI KoM.~L SINGH ( Alternate ) SHRI K. THIRUVENKADATHAN W. S. Insulators of India Ltd, Madras Srmr S. RAJAN ( Alternate ) Crompton Greaves Ltd, Bombay SHRI C. R. VARIER Da G. PARTHASARATHY ( Alternate) Director General, IS1 ( Ex-o&cio Member ) S,HRI S. P. SACHDEV, Director ( Elec tech ) SHRI K. GANESH Assistant Director ( Elec tech ), IS1 IS : 2165 ( Part 2 ) - 1983 Indian Standard INSULATION CO-ORDINATION PART 2 PHASE-TO-PHASE INSULATION CO-ORDINATION, PRINCIPLES AND RULES 0. FOREWORD 0.1 This Indian Standard ( Part 2 ) was adopted by the Indian Standards Institution on 3 August 1983, after the draft finalized by the High Voltage Techniques Sectional Committee had been approved by the Electrotechnical Division Council. 0.2 The principles governing insulation co-ordination and the standardized level of insulation of the various items of equipment used in a given electrical installation are covered in IS : 2165-1977*, now redesignated as IS : 2165 ( Part 1 )-I977 `Insulation co-ordination : Part 1 Phase-to-earth insulation co-ordination, principles and rules ( second revision )`. This standard ( Part 2 ) deals with phase-to-phase insulation of the equipment used in electric power system and is intended as a guide to equipment committees for specifying insulation levels and test procedures. 0.3 The object of this standard is to lay down the specification of phaseto-phase insulation of the equipment used in electric power systems. Each apparatus committee is responsible for specifying the insulation level and test procedures suitable for its equipment, recognizing the For the tests prescribed in recommendations given in this standard. this standard, the values of the rated withstand voltages shall be chosen from the standardized insulation levels specified in this standard. 0.4 In the preparation of this standard, assistance has been derived from IEC Pub 71-3 (1982) `Insulation co-ordination : Part 3 Phase-to-phase insulation co-ordination, principles, rules and application guide' issued by the International Electrotechnical Commission. 0.5 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test, shall be rounded off in accordance with of significant places retained in the IS : 2-19607. The number rounded off value should be the same as that of the specified value in this standard. *Insulation co-ordination ( second reuision ). TRules for rounding off numerical values ( revised ). 3 IS : 2165 ( Part 2 ) - 1983 1. SCOPE 1.1 This standard ( Part 2 ) applies to equipment for three-phase ac systems, with a highest voltage for equipment above 1 kV. It does not apply to equipment on which the different phases are separated by metal barriers. It covers phase-to-phase insulation. 2. TERMINOLOGY 2.1 For the purpose of this standard, ( Part 1 ) - 1977* shall apply. 3. BASIC PRINCIPLES the definitions given in IS : 2165 3.1 Range of Highest Voltages for Equipment - In accordance with IS : 2165 ( Part 1 )-1977* the standard values for the highest voltage for equipment are divided into three ranges. Range Range Range 3.2 A B C Above From 1 kV and Iess than 52 kV 52 kV to less than 300 kV 300 kV and above Tests suitably range. for each combination The three categories of of Selection of the Dielectric 3.2.1 The electric tests are the insulation category and insulation are: a) External b) External c) Internal 3.2.2 apply: a) Ranges A and B For the air insulation, insulation insulation. selection of selected voltage with insulators, dielectric and following criteria shall tests the The performance under power-frequency operating voltage and temporary overvoltages is checked by a short duration phase-tophase power-frequency test. The performance under switching overvoltages is checked by a phase-to-phase lighting impluse and short duration power-frequency test. The performance under lighting overvoltages is checked by a phase-to-phase lightningimpulse test. The procedure for these tests is described in 7.1. principles *Insulation co-ordination and rules ( second revision ). : Part 1 Phase-to-earth 4 insulation co-ordination, IS : 2165 ( Part 2 ) - 1983 In some cases it may be necessary to assess the influence of contamination on external insulation with insulators by a special The performance and voltage level of the power-frequency test. test is to be specified by the relevant apparatus committees. b) Range C In this voltage a in or it range the performance of insulation is verified by phase-to-phase switching-impulse test which is described 7.2. If, for special reasons, a phase-to-phase lightning-impulse power frequency test is advisable for some kind of insulation, should be specified by the relevant apparatus committee. In some cases it may be necessary to assess the influence of contamination on external insulation with insulators by a special power-frequency test. The performance and voltage level of the test is to be specified by the relevant apparatus committees. 4. STANDARD EQUIPMENT PHASE-TO-PHASE IN RANGE A INSULATION LEVELS FOR 4.1 General Indications - The following clause specifies phase-tophase insulation levels associated with standard values of the highest voltage for equipment in range A. These levels are identical with those given in IS : 2165 ( Part 1 )-1977*. 4.2 Standard Phase-to-Phase Insulation Levels - The standard insulation levels are given in Table 1. The choice of the power frequeney dry and wet test shall be made in accordance with IS : 2165 ( Part 1 )-1977*. Intermediate values shall not be employed. 5. STANDARD EQUIPMENT PHASE-TO-PHASE IN RANGE B INSULATION LEVELS FOR 5.1 General 5.1.1 The associated range B. Indications following clause specifies phase-to-phase with standard values of the highest voltage insulation levels for equipment in 5.1.2 The components of insulation levels, that is rated impulse and rated short duration power-frequency withstand are selected from those given in IS : 2165 ( Part 1 )-1977*. ples and rules ( second revision ). lightning voltages *Insulation co-ordination : Part 1 Phase-to-earth insulation co-ordination, princi- 5 IS : 2165 ( Part 2 ) - 1983 TABLE 1 STANDARD PHASE-TO-PHASE INSULATION LEVELS FOR 1kV < Vm[ < given in IS : 2165 ( Part 1 )-1977* ] are, in some cases, inadequate to ensure withstand of phase-to-phase temporary overvoltages. switching overvoltages or phase-to-phase They may, however, be used where a detailed study of a particular system shows that these overvoltages are usually low. The values of the power frequency levels shown in brackets in Table 2 are the The lowest values associated with each highest lowest that can be recommended. voltage for equipment are close to a temporary overvoltage of I.5 p. u., and their application presumes a check of the temporary and switching overvoltages in the system. ( Conlinued ) IS : 2165 ( Part i ) - 1983 TABLE 2 STANDARD PHASE-TO-PHASE INSULATION 52 kV < Urn < 300 kV - Condd LEVELS FOR The values of lightning impulse withstand voltages shown in brackets are not recommended for general use but may be employed where the appropriate lightning overvoltage protection to earth is provided and the reduction confers an economic advantage. In this case, combination of lightning impulse and short duration powerfrequency withstand voltages other than that indicated in Table 2 may be applied. In any case, it is recommended that both phase-to-phase and phase-to-earth performances are checked simultaneously by a single set of tests. Where lower lightning impluse withstand levels to earth than phase-to-phase are applied, however, the relevant apparatus committees have to specify the combination of phase-to-earth_ and phase-to-phase test levels, including the test procedure. other than. those given in Table 3 are technically justifiable the value shall be selected from the series ( Part 1 )-1977*. and economically given in IS : 2165 6.1.2 The rated switching impulse withstand voltages for phase-tophase insulation have been calculated on the basis of the rated switching impulse withstand voltages to earth and in accordance with IS : 371619787. 6.2 Standard Phase-to-Phase Insulation Levels the highest withstand 6.2.1 Table 3 lists the recommended combinations of voltages for equipment and the rated switching-impulse voltages for phase-to-earth and phase-to-phase insulation. 6.2.2 To simulate the stress situation in the network, the switchingimpulse test for phase-to-phase insulation is made by using two voltages Both components shall be components having opposite polarities. applied simultaneously, the negative one on one phase, the positive one on the other phase ( see 7 ). 6.2.3 For the test of external insulation, the amplitudes of both components shah be equal and half the values of the rated switching impulse insulation level for phase-to-phase insulation ( see IS : 37161978t ). 6.2.4 For the test of internal insulation of apparatus, the amplitudes of the two components may be specified by the relevant apparatus committees, provided that the sum of the two components shall be chosen< from the standardized insulation levels specified in Table 3. NOTE - The choice of the two components is influenced by the kind of internal: insulation used and by the type of apparatus ( for example, transformers with magnetically coupled phases ). *Insulation co-ordination : Part 1 Phase-to-earth insulation co-ordination, and rules ( second reuision ). tApplication guide for insulation co-ordination (first revision ). principles. 8 IS : 2165 ( Part 2 ) - 1983 6.2.5 Lightning-impulse not required in range C. sidered for special cases. TABLE 3 STANDARD tests for phase-to-phase insulation are normally However, the remarks in 3 should be con- PHASE-TO-PHASE INSULATION FOR Urn 2 300 kV 6.2.1 and6.2.4) RATED SWITCHINGl IMPULSE WITHSTAND VOLTAGE TO EAETH ( peak 1 (3) kV LEVELS (Cluuses6.1.1, HIGHEST VOLTAGE FOR EQUIPMENT .um BASE FOR P:U. VALUES RATED SWITCHING IX~ULSE WITHSTAND VOLTAQE PHASE-TO-PHASE (rms) ( peak ) 9) kV 245 ( peak ) (4) p.Ll. ( peak ) (5) kV 1 175 1 300 1 300 1 425 1 425 1 550 1 675 1 800 2 250 2 400 2 550 ( peak 1 (6) P.U. 4.80 5.31 439 4'81 415 4'52 3.90 420 3.60 3.84 408 (1) kV 300 362 420 525 765 750 850 850 950 950 1 050 1 050 1 175 3.06 3.47 2.86 3.21 2.76 3.06 2.45 2.74 2.08 2.28 2.48 296 343 429 625 1 300 1 425 1 550 6.3 Power-Frequency Insulation Levels 6.3.1 Power frequency tests may be required to check the performance of the insulation in normal service and under temporary overvoltages as The temporary phase-to-phase described in IS : 2165 ( Part 1 )-1977*. overvoltages should then be assumed not to exceed I.5 Urn under normal circumstances and their duration shall not exceed one second on each occasion that they occur. Tests and test conditions should be specified by the relevant apparatus committees. *Insulation co-ordination and rules ( second revision ). : Part 1 Phase-to-earth insulation co-ordination, principles 9 IS : 2165 ( Part 2 ) - 1983 7. GENERAL 7.0 General 7.0.1 Reference is made to the recommendations given in IS : 2165 and to the relevant portions in IS : 2071 ( Part 1 )( Part 1 )-1977*, 1974?. For external insulation, the tests are made under dry conditions. If, however, insulators between phases are involved in outdoor external insulation, wet tests should be taken into consideration for powerfrequency and switching impulse tests. 7.1 Lightning impulse and short for phase-to-phase insulation. 7.1.0 These tests are applicable duration power frequency A and B. tests TESTING PROCEDURE mainly in the Ranges 7.1.1 If the external insulation is to be tested between phases, the lightning impulse voltage or the short duration power-frequency is applied to one phase while adjacent phases are earthed. Phase- to-phase principle to this method. Special tests on apparatus conform in recommendations may, however, be defined by the relevant apparatus committees. 7.1.2 The standard lightning impulse has a front time of 1.2 ps and a time-to-half-value of 50 ps as specified in IS : 2071 ( Part 2 )-1974:. 7.2 Switching insulation. 7.2.0 These impulse tests apply withstand to range C. impulse voltage has a time-to-peak of of 2 500 ps as specified in IS : 2071 committee may specify a different testthat this is necessary to establish the apparatus, or where the standard for a particular test object. tests for phase-to-phase 7.2.1 The standard switching 250 ps and a time-to-half value The apparatus (Part 2 )-1974:. impulse shape where it is shown lowest withstand of a particular impulse shape cannot be obtained 7.2.2 The test shall be performed with two switching impulse generators producing two voltage components with simultaneous peaks the values of which are specified in 6.2, using the positive component at one phase and the negative component at the other. 7.2.3 For external insulation, the applied positive components should always have a time to peak of 250 /.G as specified in IS : 2071 ( Part 2 )This is the same as for phase-to-earth tests. The time-to-peak 1974$. ofthe negative component has a negligible influence; it must, however, *Insulation co-ordination : Part 1 Phase-to-earth insulation co-ordination, principles and rules ( second revision ). jMethods of high voltage testing : Part 1 General definitions and test requirements ( Jirst w&ion ) . *Methods of high voltage testing : Part 2 Test procedures (Jir~t revision ). 10 IS : 2165 ( Part 2 ) - 1983 be equal to or longer than that of the positive component. Therefore, the negative switching impulse component can be as an alternative, generated by an impulse-excited transformer. If the time-to-peak of the negative component is longer than that of the positive one, the positive component may cause a visible distortion ( voltage drop ) on the negative component due to capacitive coupling. This voltage drop shall not exceed 20 percent of the prospective peak value of the negative component. At the instant of the positive component peak, the actual voltage of the negative component should be equal to the required value. 7.2.4 The arrangement for the phase-to-earth and phase-to-phase test should be representative of the service conditions. The test has to be performed on one or more pairs of adjacent phases depending on the degree of geometric asymmetry of the actual three-phase arrangement. If the third phase is present in the test arrangement it should be earthed. During testing of any pair of adjacent phases, the positive voltage component shall be applied successively to both phases in order to take into account the lowest dielectric strength, unless it is evident that one test is sufficient. 7.2.5 The testing procedure refers .and is not a substitute for phase-to-earth to phase-to-phase tests. insulation only 11 INDIAN ON HIGH IS: 1876-1961 STANDARDS VOLTAGE TECHNIQUES Method for earthed ) voltage measurement by means of sphere-gaps Part 1 General Part ( one sphere drfiniticns and (first 2071 ( Part 1 )-I974 Methods of high voltage test requirements ( jkt revision ) 2071 ( Part 2 )-I974 revision ) 2071 ( Part 3 )-1976 revision ) 2165 ( Part 1 )-1977 3716-1978 6209-1982 8690-1977 Application Methods Methods Methods Insulation of high of high voltage voltage testing: testing: 2 Test prcccdurcs testing: Part 3 Measuring Part 1 ( second revision ) (first revi>ion) devices (Jht co-ordination, guide for insulation co-ordination for partial discharge;measurements ( jrst rcriCon ) testing Application guide for measuring devices for high voltsge